renderer: block screen shader on screencopy

src/render/OpenGL.hpp

@@ -112,6 +112,7 @@ struct SCurrentRenderData {
     bool                mouseZoomUseMouse  = true; // true by default
     bool                useNearestNeighbor = false;
     bool                forceIntrospection = false; // cleaned in ::end()
+    bool                blockScreenShader  = false;
 
     Vector2D            primarySurfaceUVTopLeft     = Vector2D(-1, -1);
     Vector2D            primarySurfaceUVBottomRight = Vector2D(-1, -1);